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Physics Unit 3
Key Words from Physics Unit 3
Term | Definition |
---|---|
Ultrasound | Sound with a higher frequency than we can hear (above 20 000 Hz). |
Refractive Index | A measure of how much a substance can refract a light ray. |
Critical Angle | When the angle of refraction is increased until the refracted ray emerges along the boundary. |
Converging Lens | A lens that makes light rays parallel to the principal focus converge at a point. |
Focal Length | The distance from the centre of a lens to the point where light rays parallel to the principal axis are focused. |
Real Image | An image formed by a lens that can be projected on a screen. |
Ciliary Muscles | Attached to the lens by suspensory ligaments. The Ciliary muscles change the thickness of the eye lens. |
Retina | The light sensitive cells around the inside of the eye |
Cornea | Transparent layer that protects the eye and helps to focus light on to the Retina. |
Iris | Coloured ring of muscle that controls the amount of light entering the eye. |
Pupil | The central hole formed by the Iris. Light enters the eye through the Pupil. |
Short-sighted | When the uncorrected image is formed in front of the Retina instead of on the Retina. The eye muscles can not make the eye lens thin enough. You use a Diverging lens to correct it. |
Long-sighted | When the uncorrected image is formed behind the Retina. The eye lens can not be made thick enough. You use a Converging lens to correct it. |
Lens Power | Measured in the Dioptre. |
Endoscope | Used to see inside the body directly. |
Diverging Lens | Makes parallel rays spread out. |
Virtual Image | Formed by a diverging lens and, if the object is nearer to the lens than the principal focus, by a converging lens. |
Moment | The turning effect of a force. |
Charge-coupled Device (CCD) | Used to record and display an image. |
Total Internal Reflection | Occurs when the angle of incidence of a light ray in a transparent substance is greater than the critical angle. |
Principle Of Moments | For an object to be in equilibrium, the sum of all the clockwise moments about any point must = the sum of the total anti-clockwise moments about that point. |
Centre Of Mass | The point where an object's mass may be thought to be concentrated. |
Centripetal Force | The resultant force towards the centre of a circle acting on an object moving in a circular path. |
Hydraulic System | |
Time Period | The time taken for one complete cycle of oscillating motion. |
Frequency | The number of wave crests passing a fixed point every second. |
Motor Effect | When a current is passed along a wire in a magnetic field and the wire is not parallel to the lines on the magnetic field, a force is exerted on the wire by the magnetic field. |
Electromagnetic Induction | The process of inducing a potential difference in a wire by moving the wire so it cuts across the lines of a force of a magnetic field. |
Near Point Of Human Eye | The nearest point to an eye at which an object can be seen in focus by the eye. (Usually 25cm) |
Blind Spot |